Fires in aircraft cargo holds are difficult to detect before they reach the stage where they endanger the safety of the aircraft. Sometimes they break out in the bottom of the hold, generating primarily smoke and other gases with little or no visible flames or heat for a considerable length of time. In addition, optical cargo hold detectors often generate xe2x80x9cnuisancexe2x80x9d alarms due to dust or moisture condensation inside the detector chamber. For this latter reason, it is felt that gas sensing detectors in combination with smoke detectors are preferable since this combination can discriminate between nuisance alarms and real fires.
A complication with gas sensing detectors is that due to the mix of materials in the hold, the composition of the gases generated by a fire can vary over wide ranges. Thus the detector manufacturers do not know what they must design their systems to respond to. There are prior art standards for smoke detectors but they are based on tests using shredded newspaper, wood, or flammable liquids as the burning substances. In passenger aircraft, however, the holds are filled primarily with luggage; thus the fires are initially fed by the synthetic plastics used in making the luggage and its contents.
Since luggage and its contents (clothing, consumer packaging, etc.) can be made from many different plastics, and each has its own characteristic products of combustion, allowing each detector manufacturer to use a different combustion test sample would lead to an undesirable variation in the types of detectors.
In addition, it is difficult to design a single detector that is effective with both smoldering and flaming fires, and it is likewise difficult to design a test setup that can simulate either type of fire.
Accordingly, it is an object of the present invention to provide a reference combustion test sample.
It is a further object of the present invention to provide a reference combustion test sample that generates, as closely as possible, the same mixture of products of combustion as would be found in a fire in an aircraft cargo hold.
It is a further object of the present invention to provide a reference combustion test sample that is easily prepared and easy to use.
It is a further object of the present invention to provide a reference combustion test sample that gives reproducible results.
It is a further object of the present invention to provide a reference combustion test sample that can be used to simulate both smoldering and flaming fires.
It is a further object of the present invention to provide a method of using a reference combustion test sample in a manner that simulates both smoldering and flaming fires.
Briefly, the present invention is a reference combustion test sample that is comprised of pellets of different types of plastics that have been heated to fuse them into a porous unitary mass. A heating element is incorporated into the sample. When the heating element is energized it causes the sample to smolder, thereby simulating the atmosphere in a cargo hold when there is a smoldering fire in it. In addition, a flammable liquid can be placed on the sample and ignited simultaneously with the energization of the heating element to simulate a flaming fire.